The Eads Bridge is a steel technology combined road and railway bridge over the Mississippi River at St. Louis, connecting St. Louis and East St. Louis, Illinois. Opened in 1874, it was one of the earliest long bridges built across the Mississippi, the world' first all steel construction, and built high enough so steamboats could travel under. As such, the St. Louis Landmark is listed on the U.S. National Register of Historic Places, as a U.S. National Historic Landmark. As of April 2014, it carries about 8,100 vehicles daily, down 3,000 since the new Stan Musial Veterans Memorial Bridge opened in February 2014.The bridge is named for its designer and builder, James B. Eads. When completed in 1874, the Eads Bridge was the longest arch bridge in the world, with an overall length of 6,442 feet (1,964 m). The ribbed steel arch spans were considered daring, as was the use of steel as a primary structural material: it was the first such use of true steel in a major bridge project. The cost of building the bridge was nearly ten million dollars.The Eads Bridge was also the first bridge to be built using cantilever support methods exclusively, and one of the first to make use of pneumatic caissons. The Eads Bridge caissons, still among the deepest ever sunk, were responsible for one of the first major outbreaks of "caisson disease" (also known as "the bends" or decompression sickness). Fifteen workers died, two other workers were permanently disabled, and 77 were severely afflicted.